The investigators propose to construct fiberoptic sensors to detect directly antibodies against HIV within several minutes. A monolayer of HIV antigen peptides will be bonded to a short section of fiber. Antigen bonding will be achieved through addition of amino group functionality to the silicon oxide fiber core and subsequent crosslinking of antigen peptides to the amino groups through cysteine residues in the peptide. Antibody binding to the antigen molecules will be directly detected by changes in optical adsorption or fluorescence. The peptide selected for construction of the first sensor contains 21 amino acids from the gp41 envelope glycoprotein of the virus. This peptide has one cysteine for crosslinking, and has been found to bind HIV antibodies in all infected individuals examined, while showing no binding to multiple control sera. For initial testing of antibody binding to fiber sensor, rabbit antisera against the antibody peptides will be utilized. The attachment of the antigen will employ techniques developed by groups in the biochemistry and biosensor laboratories of Case Western Reserve University. This work will ultimately lead to fiberoptic sensors which can be used in a physician's office for direct testing for HIV infection.